Ethernet via Thunderbolt display with MacBook Pro 2017 (A1707)?

Solution 1:

It looks like this other post provided the hint that I needed to get this working! MacBook Sierra display ethernet needs constant re-starting

Unplugging the display and then plugging it back in fixed the problem! What a pain!

Solution 2:

According to this the trick is:

To get the ethernet on the display working, I had to disconnect the USB-C adapter, delete (AFAIR) the Thunderbolt Bridge from the network preferences, and then reconnect the adapter.

This worked for me too, I now have Display Ethernet in the network interfaces list.